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BY-NC-ND 4.0 license Open Access Published by De Gruyter October 24, 2022

Terminology for chain polymerization (IUPAC Recommendations 2021)

  • Christopher M. Fellows ORCID logo , Richard G. Jones ORCID logo , Daniel J. Keddie ORCID logo , Christine K. Luscombe ORCID logo , John B. Matson ORCID logo , Krzysztof Matyjaszewski ORCID logo , Jan Merna ORCID logo , Graeme Moad ORCID logo EMAIL logo , Tamaki Nakano ORCID logo , Stanislaw Penczek ORCID logo , Gregory T. Russell ORCID logo and Paul D. Topham ORCID logo

Abstract

Chain polymerizations are defined as chain reactions where the propagation steps occur by reaction between monomer(s) and active site(s) on the polymer chains with regeneration of the active site(s) at each step. Many forms of chain polymerization can be distinguished according to the mechanism of the propagation step (e.g., cyclopolymerization – when rings are formed, condensative chain polymerization – when propagation is a condensation reaction, group-transfer polymerization, polyinsertion, ring-opening polymerization – when rings are opened), whether they involve a termination step or not (e.g., living polymerization – when termination is absent, reversible-deactivation polymerization), whether a transfer step is involved (e.g., degenerative-transfer polymerization), and the type of chain carrier or active site (e.g., radical, ion, electrophile, nucleophile, coordination complex). The objective of this document is to provide a language for describing chain polymerizations that is both readily understandable and self-consistent, and which covers recent developments in this rapidly evolving field.

1 Introduction

The objective of this document is to provide a language for describing the many forms of chain polymerization that is both readily understandable and self-consistent. Many terms from the ‘Glossary of terms related to kinetics, thermodynamics, and mechanisms of polymerization’ [1] and the ‘Terminology for reversible-deactivation radical polymerization’ documents [2] are replicated here, sometimes with additional explanatory notes, for the purposes of endorsing their continued usage. It should be stressed that it is not the intention of this document to modify any of those terms except to correct minor errors and inconsistencies as noted.

The present term “chain polymerization” to describe processes for growth of a polymer chain that proceed by a chain reaction where the propagation steps are reaction(s) between monomer(s) and active site(s) with regeneration of the active site(s) after each monomer addition was introduced in 1994 [3] in response to the conflicting literature usage and contradictory explanations that prevailed at that time for the terms “chain-growth polymerization” and “step-growth polymerization”. The terms polyaddition and polycondensation were introduced at the same time [3] for the naming of polymerizations proceeding through reactions between molecules of all degrees of polymerization. The current IUPAC terminology describing overall polymerization mechanisms is summarized in Table 1. Note that there is no group term that embraces polyaddition and polycondensation. The terms “step polymerization” and “step-growth polymerization” are deprecated by IUPAC. This issue is being considered by a current IUPAC task group [4, 5].

Table 1:

IUPAC terminology for polymerization mechanisms [3].

Propagation reaction type Polymerization reaction type Polymerization mechanisma
chain reaction; monomer units added one at a time to active site(s) with regeneration of the active site(s) functional groups on bifunctional (or greater) molecules react with each other to form new bifunctional (or greater) molecules with same functionality
chain (reaction) polymerizationb mostly non-chain (reaction) polymerizationc
addition reaction [6] [without formation of small molecule(s)] addition polymerization (additive) chain (reaction) polymerization polyaddition
condensation reaction [6] [with formation of small molecule(s)] condensation polymerization condensative chain (reaction) polymerization polycondensation
  1. aWords in parentheses are omitted in the recommended terms but are shown here to aid understanding. bChain polymerization is both a group term and a specific term for those chain polymerizations where the discrete propagation steps are addition reactions, namely (additive) chain (reaction) polymerization. The adjective “chain” in chain polymerization, which is short for “chain reaction”, must not be confused with the noun “chain” in polymer chain, a synonym for macromolecule. cWhile deprecating the term “step polymerization” or “step-growth polymerization” in 1994 [3], IUPAC did not propose a group term for non-chain (reaction) polymerizations that encompasses both polyaddition and polycondensation. The term “non-chain (reaction) polymerization” used here does not have official status (see text).

This document does not specifically consider the additional terminology associated with the formation of copolymers or different polymer architectures. It also does not consider polymers that are synthesized as a series of discrete reaction steps. These steps may be chain reactions (as in RAFT single-unit monomer insertion), chain polymerizations (as in multi-block copolymer synthesis) or condensation reactions (as in solid-state peptide synthesis). These processes might be considered as interrupted chain polymerizations, to the extent that the overall process comprises the sequential addition of monomer units to an active site.

The terms appear in alphabetical order within each section and are consecutively numbered throughout the document.

2 Terms relevant to chain polymerization

This section provides definitions of chain polymerization and various classes of chain polymerization that differ according to what reactions constitute propagation (e.g., cyclopolymerization – when rings are formed, condensative chain polymerization – when propagation is a condensation reaction, ring-opening polymerization – when rings are opened), whether they involve a termination step (e.g., living polymerization – when termination is absent, reversible-deactivation polymerization), whether a chain transfer step is involved (e.g., degenerative-transfer polymerization). It also gives the IUPAC definition for chain reaction.

CP-1 activated-monomer polymerization (AMP)

Chain polymerization in which propagation involves reaction between a growing chain-end and an activated monomer [1].

  1. Examples include the anion-activated polymerization of lactams, the cation-activated polymerization of cyclic ethers, and the Lewis acid-activated polymerization of lactones.

  2. The activator in activated-monomer polymerization should not be referred to as a catalyst unless it is established that it is a catalyst.

See activated-monomer, cation-activated-monomer polymerization, anion-activated-monomer polymerization.

CP-2 chain polymerization

Chain reaction in which the growth of a polymer chain proceeds exclusively by reaction(s) between monomer(s) and active site(s) on the polymer chain with regeneration of the active site(s) at the end of each growth step [1].

  1. A chain polymerization consists of chain initiation and chain propagation reactions, and may also include chain deactivation or chain-transfer reactions, or both.

  2. The adjective “chain” in chain polymerization denotes “chain reaction” rather than a “polymer chain”.

  3. Propagation in chain polymerization usually occurs without the formation of small molecules. When a low-molar-mass by-product is formed, the additional adjective “condensative” is recommended to form the term condensative chain polymerization.

  4. The growth steps are expressed by Px + M → Px+1 (+L) x  {1,2,…∞} where Px denotes a growing chain of degree of polymerization x, M a monomer, and L a low-molar-mass by-product formed in the case of condensative chain polymerization.

  5. The term “chain polymerization” may be qualified further, if necessary, to specify the type of chemical reactions involved in the growth step, e.g., ring-opening chain polymerization, cationic chain polymerization.

  6. There exist polymerizations that proceed via chain reactions that are not chain polymerizations. For example, the polymerization HS–X–SH + H2C=CH–Y–CH=CH2 → (–S–X–S–CH2–CH2–Y–CH2–CH2–)n proceeds via a radical chain reaction with intermolecular transfer of the radical site. The growth step, however, involves reactions between molecules of all degrees of polymerization and, hence, the polymerization is classified as a polyaddition. If required, the classification can be made more precise and the polymerization described as a chain-reaction polyaddition.

  7. the term reactive sites, used in [7, 8], was replaced with the term active sites [1].

See also condensative chain polymerization.

CP-3 chain reaction

A reaction in which one or more reactive reaction intermediates (frequently radicals) are continuously regenerated, usually through a repetitive cycle of elementary steps (the propagation step) [9, 10]. For example, in the chlorination of methane by a radical mechanism, Cl· is continuously regenerated in the chain propagation steps:

Cl+CH4HCl+H3CPropagationstepsH3C+Cl2CH3Cl+Cl

In chain polymerization reactions, reactive intermediates of the same types, generated in successive steps or cycles of steps, differ in relative molecular mass, as in:

RCH2CHPh+H2C=CHPhRCH2CHPhCH2CHPhPropogationsteps

CP-4 controlled polymerization

Term indicating control of a certain kinetic feature of a polymerization or structural aspect of the polymer molecules formed, or both [1, 2].

  1. The expression “controlled polymerization” is sometimes used to describe a radical or ionic polymerization in which reversible deactivation of the chain carriers is an essential component of the mechanism, interrupting the propagation to secure control of one or more kinetic features of the polymerization or one or more structural aspects of the macromolecules formed, or both.

  2. The expression controlled radical polymerization is sometimes used to describe a radical polymerization conducted in the presence of reagents that lead to, e.g., atom-transfer radical polymerization (ATRP), aminoxyl-mediated radical polymerization (AMRP), or reversible-addition-fragmentation chain transfer (RAFT) polymerization.

  3. Generally, the adjective “controlled” should not be used without specifying the particular kinetic or structural feature that is subject to control.

See also controlled radical polymerization, controlled ionic polymerization, controlled anionic polymerization, controlled cationic polymerization.

CP-5 cyclopolymerization

A polymerization in which the number of cyclic structures in the constitutional units of the resulting macromolecules is larger than in the monomer molecules [1].

CP-6 degenerative-transfer polymerization (DTP)

degenerate-transfer polymerization

Reversible-deactivation polymerization in which the deactivation of the active species involves degenerative chain transfer.

  1. This term has often been specifically associated with degenerative chain-transfer radical polymerization. However, there are also degenerative chain-transfer processes involving non-radical mechanisms (e.g., cationic, anionic, or coordination polymerization).

See also degenerative chain transfer, degenerative chain-transfer radical polymerization.

CP-7 group-transfer polymerization (GTP)

Chain polymerization in which a specific atom or group is intramolecularly transferred to remain associated with the active chain-end during the course of polymerization.

  1. Group-transfer polymerization is most often a reversible-deactivation polymerization or a coordination addition polymerization.

  2. The term group-transfer polymerization is often specifically associated with polymerization of (meth)acrylates and acrylamides initiated by silyl ketene acetals such as 1-methoxy-2-methyl-1-(trimethylsiloxy)prop-1-ene (traditional name is methyl trimethylsilyl dimethylketene acetal) and catalysed by nucleophiles.

  3. Other forms of chain polymerization commonly referred to as group-transfer polymerizations include catalyst-transfer polymerization and rare-earth-mediated or lanthanide-mediated coordination polymerization.

See also anionic group-transfer polymerization, catalyst-transfer polymerization, rare-earth-mediated coordination-addition polymerization.

CP-8 insertion polymerization

polyinsertion

Chain polymerization in which monomer units are sequentially inserted into a specific site within a polymer structure with retention of chain-end functionality.

  1. The term insertion polymerization is most commonly used in the context of coordination polymerization but is occasionally also used to describe some forms of reversible-deactivation radical polymerization such as RAFT polymerization and aminoxyl-mediated radical polymerization.

  2. The term polyinsertion is almost exclusively used in the context of coordination polymerization

See also coordination-insertion polymerization.

CP-9 living polymerization

deprecated: pseudo-living polymerization

deprecated: quasi-living polymerization

deprecated: immortal polymerization

deprecated: “living polymerization”

Chain polymerization in which chain termination and irreversible chain transfer are absent [1, 2].

  1. In many cases, the rate of chain initiation is fast compared with the rate of chain propagation, so that the number of kinetic-chain carriers is essentially constant throughout the reaction. This is not a necessary condition for living polymerization.

  2. In a living polymerization, the reversible (temporary) deactivation of active sites can take place (see reversible chain deactivation).

  3. In a living polymerization, all the macromolecules formed possess the potential for further growth.

  4. Use of adjectives, such as pseudo-living, quasi-living or immortal, or the use of living polymerization within quotation marks, to describe a process that shows some living characteristics, but is not living, is deprecated.

See also reversible-deactivation polymerization. Note 1 modified from [1].

CP-10 reversible-deactivation polymerization (RDP)

controlled reversible-deactivation polymerization.

Chain polymerization, propagated by chain carriers that are deactivated reversibly, bringing them into active-dormant equilibria of which there might be more than one [2].

  1. An example of a reversible-deactivation polymerization is group-transfer polymerization.

See also reversible-deactivation anionic polymerization, reversible-deactivation cationic polymerization, reversible-deactivation coordination polymerization, reversible-deactivation radical polymerization.

CP-11 ring-opening polymerization (ROP)

Polymerization in which a cyclic monomer yields a monomeric unit that is either acyclic or contains fewer rings than the cyclic monomer [1].

  1. If the monomer is polycyclic, the opening of a single ring is sufficient to classify the polymerization as a ring-opening polymerization.

CP-12 polymerization

The process of converting a monomer or a mixture of monomers into a polymer [8].

3 Non-chain polymerization

The current definitions for polyaddition and polycondensation [1, 3, 7, 8], both non-chain polymerizations, are provided here.

CP-13 polyaddition

Polymerization in which the growth of polymer chains proceeds by addition reactions between molecules of all degrees of polymerization [1, 3, 7, 8].

  1. The growth steps are expressed by

    Px + Py → Px+yx, y ∈ {1,2…∞}

    where Px and Py denote chains of degrees of polymerization x and y, respectively.

  2. The term “addition polymerization”, defined previously [11], embraced both the current concepts of polyaddition and chain polymerization, but did not include condensative chain polymerization. (See Note 3 under chain polymerization).

CP-14 polycondensation

Polymerization in which the growth of polymer chains proceeds by condensation reactions between molecules of all degrees of polymerization [1, 3, 7, 8].

  1. The growth steps are expressed by:

    Px + Py → Px+y + L x, y ∈ {1,2…∞}

    where Px and Py denote chains of degree of polymerization x and y, respectively, and L a low-molar-mass by-product.

  2. The terms “polycondensation” and “condensation polymerization”, defined previously [11], were synonymous. It should be noted that the current definitions of polycondensation and condensative chain polymerization (see Note 3 under chain polymerization) were both embraced by the previous term “polycondensation”.

4 Terms relevant to radical polymerization

A simplified mechanism for radical polymerization indicating some of the relevant terminology is presented in Scheme 1.

Scheme 1: 
          Simplified mechanism for radical polymerization. I• is a primary radical. Pn• is an active species, a propagating radical of chain length n, and contains the active centre.
Scheme 1:

Simplified mechanism for radical polymerization. I is a primary radical. Pn is an active species, a propagating radical of chain length n, and contains the active centre.

CP-15 controlled radical polymerization (CRP)

Term indicating control of a certain kinetic feature of a radical polymerization or structural aspect of the polymer molecules formed by radical polymerization, or both.

  1. The adjective “controlled” should not be used without specifying the particular kinetic or structural feature that is subject to control.

  2. The expression “controlled radical polymerization” is sometimes used as a synonym for reversible-deactivation radical polymerization (RDRP), e.g., atom-transfer radical polymerization (ATRP), aminoxyl-mediated radical polymerization (AMRP), or reversible-addition-fragmentation chain-transfer (RAFT) polymerization. This is acceptable subject to the proviso stated in Note 1.

  3. The term diffusion-controlled radical polymerization is sometimes used to indicate that the rate of termination is determined by the rate of diffusion of the active sites.

See also controlled polymerization.

CP-16 living radical polymerization

deprecated: pseudo-living radical polymerization

deprecated: quasi-living radical polymerization

deprecated: “living radical polymerization”

Radical polymerization in which chain termination and irreversible chain transfer are absent.

  1. Radical polymerizations, controlled radical polymerizations and reversible-deactivation radical polymerizations are not living radical polymerizations as there is a non-zero probability of chain termination.

  2. Examples of living radical polymerization may be certain polymerizations conducted in confined media which only allow reactions of individual propagating radicals.

  3. The term living radical polymerization can be used to refer to a hypothetical radical polymerization that occurs without chain termination.

  4. Use of the adjectives pseudo-living, quasi-living, “living” (within quotation marks) or other terms that containing the word living to describe a radical polymerization with only some living characteristics is deprecated [2].

See also controlled radical polymerization, living polymerization, reversible-deactivation radical polymerization.

CP-17 radical polymerization

Chain polymerization in which the active centres are radicals [1].

  1. Each active chain-end bears an unpaired electron.

CP-18 radical ring-opening polymerization

Radical polymerization in which a cyclic monomer yields a monomeric unit that is either acyclic or contains fewer rings than the cyclic monomer.

See ring-opening polymerization.

CP-19 reversible-deactivation radical polymerization (RDRP)

controlled reversible-deactivation radical polymerization

Chain polymerization, propagated by radicals that are deactivated reversibly, bringing them into active-dormant equilibria of which there might be more than one [2].

  1. The abbreviated term controlled radical polymerization shall be permitted, provided that its context (i.e., the nature of the control) is specified at the first occurrence.

  2. Names containing the word “living” are deprecated. Definition 84 in the kinetics document [1] stipulates that chain termination and irreversible chain transfer must be absent if a polymerization is to be regarded as living. Examples of deprecated terms include living radical polymerization, controlled/living polymerization and quasi-living polymerization.

  3. Atom-transfer radical polymerization, reversible-addition-fragmentation chain-transfer polymerization, and stable-radical-mediated polymerization all fall into this polymerization category.

  4. When the equilibria are established rapidly compared to the rate of propagation, the process may show many of the observable characteristics associated with living polymerization. One consequence of rapid equilibration is that it may become possible to exert control over the shape of the chain-length distribution, prepare polymers of low dispersity (i.e., polymers with a high degree of uniformity), and extend chains to form block copolymers, the block lengths of which are of low dispersity, by the sequential addition of monomers. Although some termination is inevitably taking place, the equilibrium between the remaining propagating radicals and dormant species is maintained.

Note 4 modified from [2].

5 Sub-classes of reversible-deactivation radical polymerization

Three classes of RDRP are distinguished according to the type activation mechanism. RDRP with unimolecular activation by dissociation of an initiator is known as stable radical-mediated polymerization (SRMP). RDRP with bimolecular activation by reaction of an initiator with an activator is known as atom-transfer radical polymerization (ATRP). RDRP with activation by degenerative chain transfer is known as degenerative chain transfer radical polymerization (DTRP).

5.1 Reversible-deactivation radical polymerization with unimolecular activation

5.1.1 Stable-radical-mediated polymerization (SRMP)

A simplified mechanism and the terminology for stable-radical-mediated radical polymerization (SRMP) is presented in Scheme 2. The term stable radical (X∙ in Scheme 2) used in the context of SRMP embraces the organometallic complexes used in cobalt-mediated radical polymerization and other organometallic-mediated radical polymerizations.

Scheme 2: 
              Simplified mechanism for stable-radical-mediated polymerization. I• is a primary radical. X• is a stable radical. Pn• is an active species, a propagating radical of chain length n.
Scheme 2:

Simplified mechanism for stable-radical-mediated polymerization. I is a primary radical. X is a stable radical. Pn is an active species, a propagating radical of chain length n.

The species referred to as “stable radicals” in the context of SRMP are not necessarily thermodynamically stable (storable-in-a-bottle) species, rather they are species that have sufficient “kinetic stability” such that they are largely unreactive towards addition to monomer under the conditions of the experiment.

Before initialization, the reaction medium for SRMP may comprise 1) a mixture of monomer(s) and the species I-X (the initiator or initializer); 2) a mixture of monomer(s), the stable radical (X·) and a source of radicals (I·); or 3) a mixture of monomer(s), a precursor to stable radical (X·) and a source of radicals (I·).

CP-20 aminoxyl-mediated radical polymerization (AMRP)

aminoxyl-mediated polymerization

deprecated: nitroxide-mediated (radical) polymerization (NMP)

Stable-radical-mediated polymerization in which the deactivation of the radicals involves reversible coupling with aminoxyl radicals [2].

  1. The term “nitroxide” is deprecated in IUPAC nomenclature. The recommended term is “aminoxyl”.

CP-21 cobalt-mediated radical polymerization (CMRP)

Reversible-deactivation radical polymerization mediated by a cobalt complex.

  1. The mechanism of cobalt-mediated radical polymerization may involve stable-radical-mediated polymerization (SRMP), degenerative chain-transfer radical polymerization, (DTRP), atom-transfer radical polymerization (ATRP) or some combination of these depending on the specific reagents and reaction conditions.

See also organometallic-mediated radical polymerization.

CP-22 iniferter process

Stable-radical-mediated polymerization where the initiator and dormant species are iniferters.

  1. Well-known examples of the iniferter process are polymerizations photoinitiated by bis(dialkylcarbamothioyl) disulfides with structure (R2NC(=S)S)2 (traditional name is tetraalkylthiuram disulfide) where the mediating agents are dialkylcarbamothioylsulfanyl radicals (R2NC(=S)S∙) and the dormant species are dithiocarbamates. In this case, both the bis(dialkylcarbamothioyl) disulfide and the derived dithiocarbamates can be iniferters.

  2. In the iniferter process the dominant mechanism for control is stable-radical mediated polymerization (SRMP) but the control mechanism may also involve degenerate chain transfer radical polymerization.

CP-23 organometallic-mediated radical polymerization (OMRP)

Reversible-deactivation radical polymerization mediated by an organometallic reagent.

  1. The best-known example of OMRP is cobalt-mediated radical polymerization, CMRP.

  2. The term organometallic-meditated radical polymerization is not usually used in describing an atom-transfer radical polymerization process.

  3. The mechanism of organometallic-meditated radical polymerization may involve stable-radical-mediated polymerization (SRMP), degenerative chain-transfer radical polymerization, (DTRP), atom-transfer radical polymerization (ATRP) or some combination of these depending on the specific reagents and reaction conditions.

Modified from [2].

CP-24 stable-radical-mediated polymerization (SRMP)

deprecated: stable-free-radical-mediated polymerization (SFRMP)

Reversible-deactivation radical polymerization in which the deactivation involves reversible coupling with stable (persistent) radicals [2].

  1. Processes known to involve stable-radical-mediated polymerization include aminoxyl-mediated radical polymerization and some forms of organometallic-mediated radical polymerization.

  2. The use of the term “free radical” is deprecated in IUPAC terminology.

  3. Initialization may involve decomposition of an initiator in the presence of monomer and the stable radical. Polymerization then starts when there is complete consumption of the stable radical.

  4. The species identified as stable radicals in stable-radical-mediated polymerization are not necessarily stable in a thermodynamic sense.

Modified from [2].

5.1.2 Reversible-addition-fragmentation radical polymerization

The mechanism of reversible-addition-fragmentation radical polymerization (RAFRP) is, in overall terms, similar to stable-radical-mediated radical polymerization. However, in RAFRP, the dormant species is a stable radical and the mediating agent or mediator is an unsaturated compound. The mechanism and some of the relevant terminology is presented in Scheme 3. Examples of mediators include certain 1,1-diphenylethenes, captodative monomers (bearing both an electron-donating and an electron-withdrawing substituent), and some carbonothioyl compounds.

Scheme 3: 
              
                Reversible-addition-fragmentation radical polymerization. I• is a primary radical. Pn• is an active species; a propagating radical on chain length n; X is the mediator; I-X• is a stable radical.
Scheme 3:

Reversible-addition-fragmentation radical polymerization. I is a primary radical. Pn is an active species; a propagating radical on chain length n; X is the mediator; I-X is a stable radical.

CP-25 reversible-addition-fragmentation radical polymerization (RAFRP)

Reversible-deactivation radical polymerization in which the dormant species is a stable (persistent) radical and the deactivation step involves reversible fragmentation.

  1. Examples of mediators that are proposed to provide control by this mechanism are certain 1,1-diarylethylenes, so-called captodative monomers, and carbonothioyl compounds. This mechanism could also contribute to the degree of control observed in RAFT polymerization.

  2. In some cases, the dormant polymer may undergo reversible coupling.

  3. Initialization usually involves decomposition of an initiator in the presence of monomer and the reagent. Polymerization commences when there is complete consumption of the mediator by initiator-derived radicals.

CP-26 carbonothioyl-mediated radical polymerization

deprecated: thiocarbonyl-mediated radical polymerization

Reversible-addition-fragmentation radical polymerization mediated by a carbonothioyl compound.

  1. The commonly used term, thiocarbonyl, is not consistent with IUPAC nomenclature.

5.2 Reversible-deactivation radical polymerization with bimolecular activation

The overall process and some of the relevant terminology of atom-transfer radical polymerization (ATRP) is shown in Scheme 4. The term ATRP as defined herein is not intended not imply a specific mechanism for reversible-deactivation radical polymerization with bimolecular activation. It is recommended that terms that indicate a specific mechanism (e.g., single-electron-transfer reversible-deactivation radical polymerization, SET-RDRP) not be used in circumstances where the mechanism is unknown or uncertain. Specific forms of ATRP that differ in the method of implementation or the type of activator used are listed in the notes to the various terms. The abbreviations listed are those that are most commonly encountered in the literature. These terms do not have the status of IUPAC definitions.

Scheme 4: 
            
              Transition metal-mediated atom-transfer radical polymerization (TM-ATRP or ATRP). I• is a primary radical. Pm• is an active species, a propagating radical of chain length m. X–Mtn/L is a deactivator (Mtn is transition metal in a higher oxidation state, L is a ligand). Mtn−1/L is an activator (Mtn−1 is a transition metal in a lower oxidation state).
Scheme 4:

Transition metal-mediated atom-transfer radical polymerization (TM-ATRP or ATRP). I is a primary radical. Pm is an active species, a propagating radical of chain length m. X–Mtn/L is a deactivator (Mtn is transition metal in a higher oxidation state, L is a ligand). Mtn−1/L is an activator (Mtn−1 is a transition metal in a lower oxidation state).

The inner-sphere electron transfer atom-transfer radical polymerization (ISET-ATRP) process, sometimes known as reversible chain-transfer-catalyzed polymerization (RTCP), has an analogous mechanism to atom-transfer radical polymerization but involves a non-metallic activator/deactivator. It is referred to here as a form of non-metal-mediated atom-transfer radical polymerization (NM-ATRP). The overall process and some of the relevant terminology for NM-ATRP is shown in Scheme 5.

Scheme 5: 
            Non-metal-mediated atom-transfer radical polymerization (NM-ATRP). I• is a primary radical. Pn• is an active species, a propagating radical of chain length n. A-X is a deactivator. A• is an activator.
Scheme 5:

Non-metal-mediated atom-transfer radical polymerization (NM-ATRP). I is a primary radical. Pn is an active species, a propagating radical of chain length n. A-X is a deactivator. A is an activator.

CP-27 atom-transfer radical polymerization (ATRP)

Reversible-deactivation radical polymerization in which the deactivation of the radicals involves reversible atom-transfer or reversible group transfer to usually, though not exclusively, transition-metal complexes.

  1. The activator is often incorrectly termed a catalyst. The term catalyst should only be used when referring to a species which is not changed as a consequence of reaction.

  2. There are various forms of ATRP that differ in details of the intimate mechanism, the reaction conditions and/or the reagents used. These include:

    1. Conventional, traditional or normal ATRP where the initial reaction mixture comprises an initiator (typically an alkyl halide) and an activator (the species on right-hand side of Scheme 4).

    2. Reverse ATRP where the initial reaction mixture comprises a conventional initiator as a source of radicals (e.g., a dialkyldiazene or a peroxide) and a deactivator (the species on left hand side of Scheme 4).

    3. AGET-ATRP (Activator Generated by Electron Transfer) where the activator is generated in situ by an electron transfer from a reducing agent at the commencement of the polymerization.

    4. ARGET-ATRP (Activator ReGenerated by Electron Transfer) where the activator is continuously regenerated by electron transfer from a reducing agent.

    5. ICAR-ATRP (Initiators for Continuous Activator Regeneration) – ARGET-ATRP where the reducing agent is a radical derived from a conventional initiator (e.g., a dialkyldiazene).

    6. SARA-ATRP (Supplemental Activators and Reducing Agents) where the polymerization commences with the activator (e.g., a zero-valent metal or an inorganic sulfite) which is a both a supplemental activator and a reducing agent for the deactivator.

    7. eATRP (electrochemically-mediated ATRP) where the activator is continuously regenerated by electrical current.

    8. photoATRP (photochemically-mediated ATRP) where the activator is continuously regenerated by photoreduction. The reduction can be facilitated by the presence of electron donors.

    9. mechanoATRP (mechanically-mediated ATRP) where the activator is continuously regenerated by mechanical forces through the use of the piezoelectric effect or ultrasound.

    10. PET-ATRP (photoinduced electron transfer ATRP) where activation involves electron-transfer from a photo-excited activator to an initiator which then dissociates to give an initiating species.

    11. O-ATRP (organic ATRP), a form of PET-ATRP where the activator is an organic photoredox catalyst.

  3. The term ATRP (unqualified) usually refers to copper-mediated ISET-ATRP.

Modified from [2].

See also inner-sphere electron transfer atom-transfer radical polymerization (ISET-ATRP), non-metal-mediated atom-transfer radical polymerization (NM-ATRP), outer-sphere electron transfer ATRP (OSET-ATRP).

CP-28 inner-sphere electron transfer atom-transfer radical polymerization (ISET-ATRP)

Atom-transfer radical polymerization where the activation step involves direct atom or group transfer.

  1. ATRP is sometimes used as a synonym for ISET-ATRP. The term ISET-ATRP can be used to specify that the mechanism of ATRP involves direct atom or group transfer as distinct from single electron transfer followed by atom or group transfer or OSET-ATRP.

See also atom-transfer radical polymerization (ATRP), outer-sphere electron transfer ATRP (OSET-ATRP).

CP-29 non-metal-mediated atom-transfer radical polymerization (NM-ATRP)

deprecated: reversible chain-transfer-catalyzed polymerization

Atom-transfer radical polymerization in which the deactivation of the radicals involves reversible atom transfer or reversible group transfer to a non-metallic reagent.

  1. The activator is often incorrectly termed a catalyst. The term catalyst should only be used when referring to a species which is not changed as a consequence of reaction being considered.

  2. NM-ATRP may be referred to as ATRP.

  3. There are various forms of NM-ATRP that differ in details of the intimate mechanism, the reaction conditions and/or the reagents used. These include:

    1. RCTP (reversible chain-transfer-catalyzed polymerization). The group transferred (X) is often iodine and examples of the activator (R-X) are certain nitrogen, phosphorus, germanium, or tin compounds, which include germanium tetraiodide and 1-iodopyrrolidine-2,5-dione (traditional name is N-iodosuccinimide). Use of the term RCTP is deprecated. The mechanism is proposed to involve inner-sphere electron transfer atom-transfer radical polymerization (ISET-ATRP).

    2. RCMP (reversible-complexation-mediated radical polymerization) where the activator (typically an alkyl amine) reacts with an initiator (typically an alkyl iodide) by molecule-assisted homolysis to form the initiating species and an activator-complex.

    3. O-ATRP (organocatalyzed atom-transfer radical polymerization). A photochemically-mediated ATRP in which an organic photoredox catalyst such as perylene, a 5,10-diaryl-5,10-dihydrophenazine or a 10-aryl-10H-phenoxazine is used as the activator. The mechanism is proposed to involve outer-sphere electron transfer atom-transfer radical polymerization (OSET-ATRP).

CP-30 outer-sphere electron transfer ATRP (OSET-ATRP)

single-electron-transfer RDRP (SET-RDRP)

deprecated: single-electron-transfer living radical polymerization (SET-LRP)

Atom-transfer radical polymerization where the activation step involves consecutive single electron transfer and atom or group transfer.

  1. The terms SET-RDRP (single-electron-transfer reversible-deactivation radical polymerization), SET-LRP (single-electron-transfer living radical polymerization), and zero-valent metal-mediated polymerization (e.g., Cu0-mediated radical polymerization) are sometimes used to describe a process where the polymerization commences with the activator in the form of a zero-valent metal, e.g., Cu0. The use of terms that might imply an outer sphere electron-transfer mechanism without evidence that the reaction proceeds by OSET-ATRP is deprecated.

  2. terms containing the phrase “living radical polymerization” are deprecated.

  3. OSET-ATRP may be referred to as ATRP.

See also atom-transfer radical polymerization (ATRP), inner-sphere electron transfer ATRP (ISET-ATRP)

CP-31 transition-metal-mediated radical polymerization

transition-metal-mediated reversible-deactivation radical polymerization

deprecated: transition-metal-mediated living radical polymerization

Reversible-deactivation radical polymerization mediated by transition-metal complexes or organometallic compounds.

  1. Transition metal mediated polymerization is an overarching term for atom-transfer radical polymerization (ATRP) and organometallic-mediated radical polymerization (OMRP). It is sometimes used as a synonym for transition-metal-mediated atom-transfer radical polymerization. This use of the term in that context without explanation is deprecated since it also includes organometallic-mediated radical polymerization.

  2. Cobalt-mediated radical polymerization is usually a form of organometallic-mediated radical polymerization (OMRP).

See atom-transfer radical polymerization, organometallic-mediated radical polymerization.

5.3 Reversible-deactivation radical polymerization with activation-deactivation by degenerative chain-transfer

The mechanism of degenerate or degenerative chain-transfer radical polymerization (DTRP) and some of the relevant terminology is provided in Scheme 6. The process is called degenerate because the species on each side of the equilibrium differ only in chain length. The mechanism of reversible-addition-fragmentation chain-transfer (RAFT) polymerization is shown in Scheme 7. It differs from the mechanism for DTRP shown in Scheme 6 in that the transfer step involves formation of a transient intermediate.

Scheme 6: 
            
              Degenerative chain-transfer radical polymerization. I• is a primary radical. Pn• is an active species, a propagating radical of chain length n. I-X is a chain-transfer agent. The dormant macromolecule, Pn-X, is a macro-chain-transfer agent.
Scheme 6:

Degenerative chain-transfer radical polymerization. I is a primary radical. Pn is an active species, a propagating radical of chain length n. I-X is a chain-transfer agent. The dormant macromolecule, Pn-X, is a macro-chain-transfer agent.

Scheme 7: 
            Simplified mechanism for radical polymerization with reversible-addition-fragmentation chain transfer (RAFT polymerization). I• is a primary radical. Pn• is an active species, a propagating radical of chain length n. I-X is a chain-transfer agent. The dormant species, Pn-X, is a macro-chain-transfer agent. I-X˙$\dot{X}$-Pn and Pm-X˙$\dot{X}$-Pn are intermediate adducts formed by radical addition to the respective chain-transfer agents.
Scheme 7:

Simplified mechanism for radical polymerization with reversible-addition-fragmentation chain transfer (RAFT polymerization). I is a primary radical. Pn is an active species, a propagating radical of chain length n. I-X is a chain-transfer agent. The dormant species, Pn-X, is a macro-chain-transfer agent. I-X˙-Pn and Pm-X˙-Pn are intermediate adducts formed by radical addition to the respective chain-transfer agents.

CP-32 degenerative chain-transfer radical polymerization (DTRP)

degenerate chain-transfer radical polymerization

Reversible-deactivation radical polymerization in which the deactivation of the radicals involves degenerative transfer (DT) of a group (or atom) [2].

  1. Examples of DT-active groups include those mentioned below under reversible-addition-fragmentation chain-transfer polymerization and certain derivatives of iodine (iodine-transfer polymerization, ITP), tellurium (organotellurium-mediated radical polymerization, TERP), antimony (organostibane-mediated radical polymerization, SBRP), or bismuth (organobismuthane-mediated radical polymerization, BIRP).

  2. Intermediate species may be present as, for example, in reversible-addition-fragmentation chain-transfer polymerization (RAFT polymerization).

CP-33 iodine-transfer polymerization (ITP)

Reversible-deactivation radical polymerization mediated by an iodo-compound.

  1. Where the initial polymerization mixture comprises a conventional initiator (e.g., a dialkyldiazene or a peroxide) and molecular iodine, the term RITP is commonly used.

See also reverse iodine-transfer polymerization.

CP-34 organobismuthane-mediated radical polymerization (BIRP)

Reversible-deactivation radical polymerization mediated by an organobismuthane compound.

CP-35 organostibane-mediated radical polymerization (SBRP)

Reversible-deactivation radical polymerization mediated by an organostibane compound.

CP-36 organotellurium-mediated radical polymerization (TERP)

Reversible-deactivation radical polymerization mediated by an organotellurium compound.

  1. The dominant mechanism of TERP thought to be degenerative chain-transfer radical polymerization (DTRP). However, at high temperature conditions or under photochemical irradiation the mechanism may involve stable-radical-mediated polymerization (SRMP).

CP-37 reverse iodine-transfer polymerization (RITP)

Iodine-transfer polymerization where the initial polymerization mixture comprises a conventional initiator (e.g., an azo-compound or a peroxide) and molecular iodine.

See also iodine-transfer polymerization.

CP-38 reversible-addition-fragmentation chain-transfer polymerization (RAFT polymerization)

Degenerate-transfer radical polymerization in which chain activation and chain deactivation involve a degenerative chain-transfer process, which occurs by a two-step addition-fragmentation mechanism [2].

  1. The term RAFT polymerization (unqualified) usually refers to polymerization mediated by a carbonothioylsulfanyl RAFT agent.

  2. There are various forms of RAFT polymerization that differ in details of the initiation mechanism, the reaction conditions and/or the reagents used. These include:

    1. Carbonothioylsulfanyl RAFT polymerization. The more commonly used term thiocarbonylthio RAFT polymerization is deprecated as it is inconsistent with IUPAC nomenclature. Examples of carbonothioylsulfanyl RAFT agents include certain dithioesters, trithiocarbonates, xanthates (dithiocarbonates), and dithiocarbamates with structure S=C(Z)−SR, where Z is aryl, alkylsulfanyl, alkyloxy, or dialkylamino, respectively, and R is a homolytic leaving group.

    2. Macromonomer RAFT polymerization where the RAFT agent is a “macromonomer” with structure CH2=C(Z)−CH2R, where Z is usually −CO2alkyl or −CO2aryl and R is a homolytic leaving group. This form of RAFT polymerization is also known as sulfur-free RAFT polymerization.

    3. MADIX (macromolecular design by interchange of xanthate) where the RAFT agent is a xanthate.

    4. PhotoRAFT polymerization where radical generation involves direct photolysis of a carbonothioylsulfanyl-RAFT agent to give an initiating species and a carbonothioylsulfanyl radical.

    5. PET-RAFT (photo-induced energy or photo-electron-transfer RAFT) polymerization where radical generation involves photo-induced energy or electron transfer from a photoredox catalyst or a photosensitizer, respectively, to a carbonothioylsulfanyl-RAFT agent which then dissociates to give an initiating species.

    6. redoxRAFT where radical generation involves ISET or OSET between the RAFT agent and a reducing agent agent to give an initiating species.

    7. eRAFT polymerization where radical generation involves electrochemical reduction of the RAFT agent either directly or through a redox mediator.

6 Terms relating to species and processes in chain polymerization

Many of the terms in this section are taken from the Kinetics Document [1], without modification unless indicated. These definitions, in a few cases, differ from those in the current Gold [6] and Purple Books [7]. A full list of those modified definitions is provided in [1].

The word “species”, that occurs in various terms, may be replaced by the type of species, e.g., radical, anion, cation, as appropriate for the context. Thus, the definition of propagating species is provided, and the definitions of propagating radical, anion, cation, etc. are implicit.

The use of the terms activator and catalyst in chain polymerization require brief discussion. A catalyst increases the rate of a reaction and is both a reactant and a product of that reaction; i.e., it is not consumed in the reaction. The catalyst or catalytic site in coordination polymerization and ring-opening metathesis polymerization (ROMP) is the coordination complex that comprises the active site. The precursors to those coordination complexes should not be called catalysts.

In ATRP chain activation-deactivation is accelerated by a redox reaction that, in some cases, may be part of a catalytic cycle. In most cases, the rate coefficient for propagation is unchanged from that in the absence of the activator. It is recommended that the term catalyst is not used to denote either the activator or deactivator in ATRP.

CP-39 activated monomer

Reactive species generated reversibly from a monomer [1].

  1. Most frequently, the activated monomer is an anionic or cationic species.

  2. Examples include a deprotonated lactam, a protonated cyclic ether, and a Lewis acid coordinated lactone.

See also activated-monomer polymerization, cationic activated-monomer polymerization, anionic activated-monomer polymerization.

CP-40 activator (in activated-monomer polymerization)

Species that coordinates with a monomer converting it to a more reactive species.

  1. Examples include a base in anion-activated-monomer polymerization of lactams and a proton in cation-activated-monomer polymerization of cyclic ethers.

  2. The definition of activator is different from that defined in the context of enzyme activation [9, 12].

CP-41 activator (in ATRP)

deprecated: catalyst (in ATRP)

Reagent that reacts reversibly with the initiator or dormant chain to form an initiating or propagating species, respectively, and a deactivator.

  1. An activator in atom-transfer polymerization (ATRP) is often incorrectly called a catalyst. The term catalyst should not be used to refer to a species that is consumed during the course of a reaction or to a species that is regenerated other than by deactivation.

  2. The definition of activator is different from that defined in the context of enzyme activation [9, 12].

CP-42 activator (in coordination polymerization)

cocatalyst (in coordination polymerization)

Species that reacts with a coordination compound converting it to an active catalyst during initialization of coordination polymerization.

  1. An example of a cocatalyst is methylaluminoxane (MAO).

  2. The definition of activator is different from that defined in the context of enzyme activation [9, 12].

CP-43 active centre (in a chain polymerization)

active site

Site on a chain carrier at which reaction occurs [1].

  1. In [7, 8] the term “reactive site” is used within the definition of chain polymerization. In [13], the terms “active center” and “active site” are defined in the context of heterogeneous catalysis

CP-44 active polymer chain

active macromolecule (in RDP)

See propagating species.

CP-45 addition-fragmentation chain transfer

Chain-transfer process that proceeds by a propagating species adding to a chain-transfer agent to form an intermediate that then fragments to provide an initiating species.

CP-46 bimolecular chain activation

bimolecular activation

See chain activation (in ATRP)

CP-47 cage effect

Term referring to reactions between reactant molecules trapped transiently in a restricted volume of molecular dimensions [1].

  1. In polymerizations, the best-known result of the cage effect is the reduced efficiency of initiation of a radical polymerization due to a fast reaction between the two radicals, formed by the homolytic dissociation of initiator, within a transient cage of molecules. The reaction occurs before the radicals are able to diffuse apart.

CP-48 catalyst

Substance that increases the rate of a reaction without modifying the overall standard Gibbs energy change in the reaction; the process is called catalysis. The catalyst is both a reactant and product of the reaction [14].

CP-49 catalyst (in coordination polymerization or ROMP)

Coordination compound that comprises the active site.

  1. Often the precursor species to the active coordination complex are incorrectly referred to as the catalyst.

CP-50 catalyst precursor (in coordination polymerization)

precatalyst (in coordination polymerization)

initiator (in coordination polymerization)

Coordination compound that by reaction with an activator or cocatalyst provides an active catalyst during initialization of coordination polymerization.

  1. Examples of catalyst precursors are certain transition metal or rare-earth metal complexes, such as titanium tetrachloride or bis(cyclopentadienyl)titanium chloride.

CP-51 catalytic chain transfer (CCT)

Chain-transfer process involving transfer of an atom or group to a reagent (the catalyst) that in turn transfers that group to a monomer to reinitiate polymerization and regenerate the original reagent.

  1. An example of polymerization with catalytic chain transfer is radical polymerization in the presence of certain square-planar cobalt complexes.

  2. Catalytic chain transfer may be observed as a side reaction in certain reversible-deactivation radical polymerizations including organometallic-mediated radical polymerization.

CP-52 catalytic chain termination

Chain termination process involving transfer of a group to a reagent (the catalyst) that in turn transfers that group to a propagating species to terminate a chain and regenerate the original reagent.

  1. Catalytic chain termination may be observed as a side reaction in certain reversible-deactivation radical polymerizations.

CP-53 chain activation

activation (in chain polymerization)

See chain reactivation.

CP-54 chain activation (in SRMP)

activation (in SRMP)

unimolecular chain activation

unimolecular activation

Unimolecular dissociation of a dormant species to form a mediating agent and a propagating species.

  1. In aminoxyl-mediated radical polymerization [nitroxide-mediated polymerization (NMP)], the dormant species is an alkoxyamine and the mediating agent is an aminoxyl radical.

  2. In organometallic-mediated radical polymerization (OMRP), the domant species and the mediating agent are organometallic species.

  3. In reversible addition-fragmentation polymerization (RAFRP), the dormant species is a stable radical and the mediating agent is a non-propagating olefin, e.g., 1,1-diphenylethylene.

  4. chain deactivation (in SRMP) is the reverse of chain activation (in SRMP).

CP-55 chain activation (in ATRP)

activation (in ATRP)

bimolecular chain activation

bimolecular activation

Reaction of an activator with a dormant species to form a deactivator and a propagating species.

  1. The activation and deactivation process may form part of a catalytic cycle. However, in general, the activator should not be called a catalyst.

  2. chain deactivation (in ATRP) is the reverse of chain activation (in ATRP).

CP-56 chain activation (in DTRP)

activation (in DTRP)

See degenerative chain transfer.

CP-57 chain carrier (in polymerization)

kinetic-chain carrier

Intermediate species bearing an active site for the propagation of a chain reaction.

  1. The propagating species and chain-transfer agent-derived species are chain carriers in polymerization.

See active centre, active polymer chain, propagating species.

Modified from [1].

CP-58 chain deactivation

deactivation

Conversion of a chain carrier into an inactive species [1].

  1. Chain deactivation, unlike chain termination, may be reversible; see reversible chain deactivation.

  2. The reverse of chain deactivation is chain activation or chain reactivation.

  3. The recommended symbol for the rate coefficient for chain deactivation in a polymerization is kdeact.

Note 3 added to the definition in [1].

CP-59 chain initiation

initiation

Chemical reaction in which chain carriers are generated [1].

  1. The recommended symbol for the rate coefficient for chain initiation in a polymerization is ki.

Note modified from [1].

CP-60 chain propagation (in a chain polymerization)

propagation

Chemical reaction between a chain carrier and a monomer that results in the growth of a polymer chain and the regeneration of at least one chain carrier [1].

  1. The recommended symbol for the rate coefficient for chain propagation in a homopolymerization is kp.

Note 1 modified from [1].

CP-61 chain reactivation

reactivation (in a chain polymerization)

chain activation

activation (in a chain polymerization)

Conversion of an inactive chain into a chain carrier [1].

  1. The term is usually used to refer to the reactivation of previously deactivated or dormant chains.

  2. Chain reactivation can be reversible or irreversible.

  3. The reverse of chain reactivation is chain deactivation.

  4. The recommended symbol for the rate coefficient for chain reactivation in a polymerization is kact.

Note 4 added to the definition in [1].

CP-62 chain termination (in a chain polymerization)

termination

irreversible chain deactivation

Chemical reaction in which a chain carrier is converted irreversibly into a non-propagating species without the formation of a new chain carrier [1].

  1. The recommended symbol for the rate coefficient for chain termination in a polymerization is kt.

  2. The term “chain deactivation” is often used to stress that, in contrast to chain termination, the formation of non-propagating species may be reversible; see chain deactivation and reversible chain deactivation.

  3. See also combination, disproportionation.

Note 1 modified from the definition in [1].

CP-63 chain transfer

transfer

Chemical reaction occurring during a chain polymerization in which an active site is transferred from a growing macromolecule or oligomer molecule to another molecule or to another site on the same molecule [1].

  1. The recommended symbol for the rate coefficient for chain transfer in a polymerization is ktr.

CP-64 chain-transfer agent (CTA)

transfer agent

Substance able to react with a chain carrier by a reaction in which the original chain carrier is deactivated and a new chain carrier is generated [1].

  1. In a polymerization, the common occurrence is that a new chain carrier of lower molar mass is generated.

CP-65 cocatalyst (in coordination polymerization)

See activator (in coordination polymerization).

CP-66 combination

Chain termination, in a chain polymerization, between two propagating macromolecules that gives rise to a single macromolecule of molar mass equal to the sum of the molar masses of the two macromolecules [1].

  1. Combination is often incorrectly called “recombination”. The term recombination should only be used to refer to the reaction, with each other, of two transient species produced from a common precursor [6].

  2. Combination is also called colligation [6], although this terminology is not commonly used in the context of chain polymerization.

CP-67 deactivator (in ATRP)

Reagent that reacts reversibly with the initiating species or propagating species to form an initiator or a dormant chain, respectively, and an activator.

CP-68 dead polymer chain

dead macromolecule (in RDP)

Polymer chain which plays no active role in the polymerization.

  1. A dead polymer chain is a chain unlikely to be activated or reactivated to form a propagating species under the polymerization conditions within the timescale of the polymerization.

  2. The products of chain termination and irreversible chain transfer comprise dead polymer chains.

CP-69 degenerate chain transfer

degenerate transfer

See degenerative chain transfer.

CP-70 degenerative chain transfer

degenerative transfer

degenerate chain transfer

degenerate transfer

Chain-transfer reaction that generates a new chain carrier and a new chain-transfer agent with the same reactivity as the original chain carrier and chain-transfer agent [1].

CP-71 disproportionation (in a chain polymerization)

Chain termination, in a radical polymerization, between two propagating macromolecules that results in two macromolecules, one carrying an unsaturated chain-end, the other carrying a saturated chain-end [1].

CP-72 dormant species

dormant polymer chain

dormant macromolecule (in RDP)

Temporarily deactivated chain carrier [2].

  1. A dormant polymer chain can be reactivated to a propagating chain under the polymerization conditions within the timescale of the polymerization.

  2. Examples of dormant species are the macroinitiator in AMRP or ATRP and the macroCTA or macroRAFT agent in RAFT polymerization.

CP-73 growing chain

See propagating species.

CP-74 inactive chain

non-propagating species

inactive macromolecule (in RDP)

Dead chains or dormant chains.

CP-75 inhibition (in polymer science)

Absence of polymerization brought about by the action of an inhibitor.

CP-76 inhibitor (in polymer science)

Additive that reacts so rapidly with the chain carrier that it reduces the observed rate of polymerization to zero [1].

  1. Long-chain macromolecules cannot be formed until virtually all the inhibitor is consumed.

  2. An ideal inhibitor causes a well-defined induction period during which time the inhibitor is consumed and there is no discernible polymerization, and after which polymerization proceeds at the same rate as in the absence of the inhibitor.

  3. In general chemical terminology, the term inhibitor is defined as a substance that diminishes the rate of a chemical reaction [1].

See also retarder.

CP-77 inifer

Substance that combines the properties of an initiator and a reversible chain-transfer agent.

  1. An example of an inifer in cationic polymerization is boron trichloride.

CP-78 iniferter

Substance that combines the properties of an initiator, a reversible chain-transfer agent and a chain terminator or reversible deactivator.

  1. Examples of iniferters in radical polymerization are bis(carbamothioylsulfanyl)disulfides with structure (R2NC(=S)S)2 (traditional name is thiuram disulfide).

  2. Some iniferters are also RAFT agents.

  3. A substance that combines the properties of a photoinitiator, a reversible chain-transfer agent and a chain terminator or reversible deactivator is known as a photoiniferter.

See iniferter process.

CP-79 initialization (in RDP)

Process for converting a starting initiator or chain transfer agent into a macro-initiator or macro-chain-transfer agent during reversible-deactivation polymerization (RDP).

  1. In RAFT polymerization, initialization is sometimes known as the pre-equilibrium step.

CP-80 initialization (in coordination polymerization or ROMP)

Process for converting a starting coordination complex or precatalyst into an active catalyst.

CP-81 initializer (in RDP)

Starting initiator or transfer agent in reversible-deactivation polymerization (RDP).

  1. Examples are a starting alkoxyamine initiator in aminoxyl-mediated radical polymerization (AMRP), a starting alkyl halide initiator in atom-transfer radical polymerization (ATRP) and a starting RAFT agent in RAFT polymerization.

CP-82 initialization efficiency (in RDP)

Efficiency of conversion of a starting initiator or transfer agent into a macro-initiator or macro-chain-transfer agent.

See also initiator efficiency for initiation of polymerization (fi).

CP-83 initiating species

Species to which monomer adds or becomes inserted to start a chain polymerization [1].

  1. An initiating species may be formed from an initiator or be the initiator itself.

  2. In radical polymerization, initiating species formed directly from an initiator are called primary radicals.

CP-84 initiation (in a chain polymerization)

See chain initiation.

CP-85 initiator

Substance introduced into a reaction system in order to cause chain initiation [1].

  1. In contrast to a catalyst, an initiator is consumed in the reaction.

CP-86 initiator efficiency (for initiation of polymerization) (f, fi)

initiator efficiency

Number of growing chains initiated divided by the number of active-centers generated from initiator molecules [1].

  1. The number of growing chains initiated is the number of initiating radicals formed. The number of active centers generated is the number of active centers that could formed be in the absence of any cage effect.

  2. In a radical polymerization, the frequency of production of propagating radicals from an initiator that provides two similar radicals is 2kdfi, where kd is the rate coefficient for initiator decomposition.

  3. In RDP the efficiency of conversion of a starting initiator into a macroinitiator may be called the initiator efficiency (see initialization efficiency).

  4. The initiator efficiency for radical generation from initiators such as dialkyl diazenes and organic peroxides (common symbol f, recommended symbol fg to distinguish from fi) is defined as the fraction of radicals that escape the cage (see cage effect) and are potentially available for reaction with a substrate (e.g., monomer) [15]. The value of fi will usually be less than fg as depending on the monomer and the monomer concentration, initiator-derived radicals may react to form products other than initiating radicals.

See also cage effect, initialization efficiency.

Notes modified from [1].

CP-87 kinetic-chain carrier

See chain carrier.

CP-88 living polymer chain

living macromolecule (in RDP)

Polymer chains that possess the potential for chain growth under the polymerization conditions.

  1. Living polymer chains comprise all active and dormant polymer chains.

CP-89 macro-chain-transfer agent (macroCTA)

macroRAFT agent (in RAFT polymerization)

Macromolecule containing chain-transfer-agent functionality

  1. The dormant species in RAFT polymerization is often referred to as a macroCTA or macroRAFT agent.

CP-90 macroinitiator

Macromolecule containing initiator functionality

  1. The dormant species in RDRP such as ATRP or SRMP is often referred to as a macroinitiator.

CP-91 mediating agent

mediator

Species that mediates polymerization in reversible-deactivation polymerization.

  1. Examples of mediating agents are the aminoxyl radical in aminoxyl-mediated radical polymerization (AMRP) and the RAFT agent in RAFT polymerization.

CP-92 non-propagating species

See inactive chain.

CP-93 primary species (in a chain polymerization)

Species that is formed from an initiator or monomer molecule and that is capable of initiating polymerization.

  1. In radical polymerization a primary radical may be formed by the action of heat, irradiation or electron-transfer.

  2. In radical polymerization, recombination of primary radicals and their reactions with other radicals leads to reduced initiator efficiency.

  3. The term “primary species” is also used to designate a species centred on a primary carbon atom, for example, an ethyl radical [1].

See also secondary species. Adapted from the definition of primary radical in [1].

CP-94 propagating species (in a chain polymerization)

active polymer chain

active macromolecule (in RDP)

growing chain

Active species formed by addition to monomer that is capable of adding further monomer.

  1. The propagating species are chain carriers in chain polymerization.

See chain carrier, active centre.

CP-95 retardation (in polymer science)

Diminished rate of polymerization brought about by the action of a retarder.

CP-96 retarder (in polymer science)

Substance that decreases the rate of a reaction [16].

  1. A retarder is distinct from an inhibitor, which is a substance that stops a reaction [16]. A retarder does not cause an induction period.

  2. In general chemical terminology, the terms retarder and inhibitor are synonomous and defined as substances that diminish the rate of chemical reactions [1].

See also inhibitor.

CP-97 reversible-addition-fragmentation chain-transfer agent (RAFT agent)

chain-transfer agent (CTA) (in RAFT polymerization)

Chain-transfer agent that provides chain transfer by a reversible-addition-fragmentation mechanism.

  1. An example of a RAFT agent is 2-cyanopropan-2-yl dithiobenzoate in the polymerization of methyl methacrylate.

  2. RAFT agents are mediating agents in RAFT polymerization.

See also RAFT polymerization.

CP-98 secondary species (in a chain polymerization)

Species formed by the rearrangement or fragmentation of a primary species that is capable of initiating a polymerization.

  1. The term “secondary species” is also used to designate a species centred on a secondary carbon atom, e.g., a propan-2-yl radical.

See primary species. Adapted from the definition of secondary radical in [1].

CP-99 stable radical (in SRMP or RAFRP)

Mediating agent in stable-radical-mediated radical polymerization with sufficient kinetic stability such that it is essentially unreactive towards addition to monomer under the conditions of the experiment.

  1. The stable radical mediating agent need not be thermodynamically stable

See stable-radical-mediated radical polymerization, chain activation (in SRMP).

CP-100 unimer

Species comprising only one monomer unit.

  1. The term is commonly used to designate a dormant species in reversible-deactivation radical polymerization (RDRP) that contains only one monomer unit.

CP-101 unimolecular chain activation

unimolecular activation

See chain activation (in SRMP).

CP-102 substitution chain transfer

Chain-transfer process that proceeds by a one-step substitution reaction.

  1. In radical polymerization the process is called homolytic substitution chain transfer and reaction is by a SH2 mechanism. An example of a chain-transfer agent that reacts by substitution chain transfer is a thiol.

7 Ionic polymerization

Ionic polymerization is an overarching term for chain polymerizations that involve ionic intermediates. Mechanisms for anionic and cationic polymerization are presented in Scheme 8 and Scheme 10, respectively. The definition for activated-monomer polymerization is also provided in this section because the activating species is most often, though not always, ionic.

Scheme 8: 
          Simplified mechanism for anionic polymerization.
Scheme 8:

Simplified mechanism for anionic polymerization.

CP-103 controlled ionic polymerization

Term indicating control of a certain kinetic feature of an ionic polymerization or structural aspect of the polymer molecules formed by ionic polymerization, or both.

  1. Generally, the adjective “controlled” should not be used without specifying the particular kinetic or structural feature that is subject to control.

  2. The term controlled ionic polymerization is sometimes used to indicate that the initiation is complete within a period that is short with respect to that for propagation such that dispersities are very low and the molar mass can be precisely predicted based on the initial reagent concentrations.

See controlled polymerization.

CP-104 ionic polymerization

ionic chain polymerization

Chain polymerization in which the active centres are ions or ion pairs [1].

CP-105 ionic ring-opening polymerization

Ionic polymerization in which a cyclic monomer yields a monomeric unit that is either acyclic or contains fewer rings than the cyclic monomer.

See ring-opening polymerization.

CP-106 living ionic polymerization

Ionic polymerization in which chain termination and irreversible chain transfer are absent.

  1. Ionic polymerizations, controlled ionic polymerizations and reversible-deactivation ionic polymerizations should not be described as living if there is a non-zero probability of chain termination or irreversible chain transfer.

See living polymerization.

CP-107 reversible-deactivation ionic polymerization (RDIP)

Reversible-deactivation polymerization in which the kinetic-chain carriers are ions.

See reversible-deactivation polymerization.

8 Nucleophilic chain polymerization

In the propagation step of nucleophilic chain polymerization (Scheme 8), the active centre behaves as a nucleophile but does not necessarily possess a formal negative charge. For example, the nucleophile may be a nitrogen or sulfur lone-pair. Anionic polymerization is an example of both a nucleophilic chain polymerization and an ionic polymerization. An example is anionic ring-opening polymerization of caprolactone (Scheme 9).

Scheme 9: 
          
            Chain-initiation and chain-propagation steps in anionic ring-opening polymerization of caprolactone.
Scheme 9:

Chain-initiation and chain-propagation steps in anionic ring-opening polymerization of caprolactone.

CP-108 anionic polymerization

Ionic polymerization in which the active centres are anions [1].

  1. The anions may be free, paired, or aggregated.

CP-109 anionic group-transfer polymerization

group-transfer polymerization (GTP)

Anionic polymerization in which a specific atom or group is intramolecularly transferred to remain associated with the active chain-end during the course of polymerization.

  1. An example is polymerization of methyl methacrylate initiated by 1-methoxy-2-methyl-1-(trimethylsiloxy)prop-1-ene (traditional name is methyl trimethylsilyl dimethylketene acetal) and catalysed by a nucleophile.

CP-110 anionic ring-opening polymerization

Anionic polymerization in which a cyclic monomer yields a monomeric unit that is either acyclic or contains fewer rings than the cyclic monomer.

  1. Some examples of monomers used in anionic ring-opening polymerization are intramolecular anhydrides of N-carboxy amino acids (commonly referred to as N-carboxy anhydrides or NCAs), epoxides and cyclic siloxanes.

See ring-opening polymerization.

CP-111 controlled anionic polymerization

Term indicating control of a certain kinetic feature of an anionic polymerization or structural aspect of the polymer molecules formed by anionic polymerization, or both.

  1. Generally, the adjective “controlled” should not be used without specifying the particular kinetic or structural feature that is subject to control.

  2. The term “controlled anionic polymerization” is sometimes used to indicate that the initiation is complete within in a period that is short with respect to the time for propagation such that dispersities are very low and the molar mass can be precisely predicted based on the initial reagent concentrations.

See controlled polymerization.

CP-112 living anionic polymerization

Anionic polymerization in which chain termination and irreversible chain transfer are absent.

  1. Anionic polymerizations, controlled anionic polymerizations and reversible-deactivation anionic polymerizations should not be described as living if there is a non-zero probability of chain termination or irreversible chain transfer.

See living polymerization.

CP-113 reversible-deactivation anionic polymerization (RDAP)

Reversible-deactivation polymerization in which the kinetic-chain carriers are anions.

  1. An example of a reversible-deactivation anionic polymerization is group-transfer polymerization of methyl methacrylate initiated by 1-methoxy-2-methyl-1-(trimethylsiloxy)prop-1-ene (traditional name is methyl trimethylsilyl dimethylketene acetal) and catalysed by a nucleophile.

  2. Another example is anionic polymerization with reversible formation of an ion-pair or a different ion cluster size.

See reversible-deactivation polymerization.

CP-114 nucleophilic chain polymerization

Chain polymerization in which the active centres are nucleophilic species.

  1. Anionic polymerization is an example of nucleophilic chain polymerization.

  2. Some examples of non-ionic nucleophilic species are nitrogen and sulfur lone pairs.

See anionic polymerization.

CP-115 ring-opening nucleophilic chain polymerization

Nucleophilic chain polymerization in which a cyclic monomer yields a monomeric unit that is either acyclic or contains fewer rings than the cyclic monomer.

  1. Examples of non-ionic monomers used in ring-opening nucleophilic chain polymerization include intramolecular anhydrides of N-carboxy amino acids (commonly referred to as N-carboxy anhydrides or NCAs).

See ring-opening polymerization.

9 Electrophilic chain polymerization

In the propagation step of electrophilic chain polymerization, the active centre behaves as an electrophile but does not necessarily possess a formal positive charge. Cationic polymerization is an example of both an electrophilic chain polymerization and an ionic polymerization.

Scheme 10: 
          Simplified mechanism for cationic polymerization.
Scheme 10:

Simplified mechanism for cationic polymerization.

CP-116 cationic polymerization

Ionic polymerization in which the active centres are cations [1].

  1. The cations may be free, paired, or aggregated.

CP-117 cationic ring-opening polymerization

Cationic polymerization in which a cyclic monomer yields a monomeric unit that is either acyclic or contains fewer rings than the cyclic monomer.

  1. Some examples of monomers used in cationic ring-opening polymerization are cyclic ethers, lactones and lactams.

See ring-opening polymerization.

CP-118 controlled cationic polymerization

Term indicating control of a certain kinetic feature of a cationic polymerization or structural aspect of the polymer molecules formed by cationic polymerization, or both.

  1. Generally, the adjective “controlled” should not be used without specifying the particular kinetic or structural feature that is subject to control.

See controlled polymerization.

CP-119 electrophilic chain polymerization

Chain polymerization in which the active centres are electrophilic species.

  1. Cationic polymerization is an example of electrophilic chain polymerization.

See cationic polymerization.

CP-120 living cationic polymerization

Cationic polymerization in which chain termination and irreversible chain transfer are absent.

  1. Cationic polymerizations, controlled cationic polymerizations and reversible deactivation cationic polymerizations should not be described as living if there is a non-zero probability of chain termination or irreversible chain transfer.

See living polymerization.

CP-121 reversible-deactivation cationic polymerization (RDCP)

Reversible-deactivation polymerization in which the chain carriers are cations.

  1. An example of a reversible-deactivation cationic polymerization is reversible ion-pair formation.

See reversible-deactivation polymerization.

10 Activated-monomer polymerization

Activated-monomer polymerizations (see CP-1 and Scheme 11) are treated separately from electrophilic chain polymerization and nucleophilic chain polymerization even though most examples also belong to one of these categories. A distinction is also made between activated-monomer polymerization, where the monomer is activated by coordination with a catalyst or activator, and coordination polymerization, where both the monomer and the propagating species form part of a coordination complex.

Scheme 11: 
          Simplified mechanism for activated-monomer polymerization. Pn* is a generic propagating species.
Scheme 11:

Simplified mechanism for activated-monomer polymerization. Pn* is a generic propagating species.

Radical polymerizations in the presence of certain Lewis acids, where the Lewis acid provides for substantial rate acceleration, might also be considered as activated-monomer polymerizations. However, the term is seldom used in this context.

The propagation reaction in activated monomer polymerization involves reaction between a propagating species and an activated monomer that is formed by coordination of an activator to a monomer.

Examples of activated monomer polymerization are the cation-activated-monomer polymerization of oxirane (Scheme 12) and caprolactone (Scheme 13), and the anion-activated-monomer polymerization of an intramolecular anhydride of a N-carboxy amino acid (commonly referred to as an N-carboxy anhydrides or NCA) (Scheme 14).

Scheme 12: 
          
            Chain-initiation and chain-propagation steps in cation-activated-monomer polymerization of oxirane where the activator is a protic acid (AH).
Scheme 12:

Chain-initiation and chain-propagation steps in cation-activated-monomer polymerization of oxirane where the activator is a protic acid (AH).

Scheme 13: 
          
            Chain-initiation and chain-propagation steps in cation-activated-monomer polymerization of caprolactone where the activator is a protic acid (AH).
Scheme 13:

Chain-initiation and chain-propagation steps in cation-activated-monomer polymerization of caprolactone where the activator is a protic acid (AH).

Scheme 14: 
          
            Chain initiation and chain-propagation steps in anion-activated-monomer polymerization of an N-carboxy anhydride (NCA) where the activator is a base. Note that nucleophilic ring-opening polymerization of N-carboxy anhydrides is not usually considered as a condensative chain polymerization because carbon dioxide is not eliminated in the propagation step, but rather in a separate step following propagation.
Scheme 14:

Chain initiation and chain-propagation steps in anion-activated-monomer polymerization of an N-carboxy anhydride (NCA) where the activator is a base. Note that nucleophilic ring-opening polymerization of N-carboxy anhydrides is not usually considered as a condensative chain polymerization because carbon dioxide is not eliminated in the propagation step, but rather in a separate step following propagation.

CP-122 anion-activated-monomer polymerization

anionic activated-monomer polymerization

Activated-monomer polymerization where the propagating species is an electrophile and activating species is anionic.

CP-123 cation-activated-monomer polymerization

cationic activated-monomer polymerization

Activated-monomer polymerization where the propagating species is a nucleophile and the activating species is cationic.

11 Ring-opening metathesis polymerization

Metathesis polymerization is a process in which unsaturated monomers are transformed into unsaturated polymers by a process of bond redistribution. When the unsaturated monomer is contained in a ring, ring-opening metathesis polymerization (ROMP) is possible.

Ring-opening metathesis polymerization commonly involves cyclic olefin monomers and a metal-carbene complex as the initiator, which is the catalytic site (catalyst) in the polymerization (Scheme 15). In most cases, the initiating metal-carbene complex is formed in situ, in which case the precursor(s) to the complex are the initiator and the active catalyst is the initiating species.

Scheme 15: 
          Simplified mechanism for ring-opening metathesis polymerization catalyzed by a metal-carbene complex. [Mt]= is a metal-carbene complex (ROMP).
Scheme 15:

Simplified mechanism for ring-opening metathesis polymerization catalyzed by a metal-carbene complex. [Mt]= is a metal-carbene complex (ROMP).

In metal-free electron-transfer ring-opening metathesis polymerization (ET-ROMP) initiation is thought to involve single electron-transfer from a vinyl ether initiator with formation of a radical cation as the initiating species and chain carrier (Scheme 16).

Scheme 16: 
          Simplified mechanism for electron-transfer ring-opening metathesis polymerization (ET-ROMP).
Scheme 16:

Simplified mechanism for electron-transfer ring-opening metathesis polymerization (ET-ROMP).

CP-124 living ring-opening metathesis polymerization

Ring-opening metathesis polymerization in which chain termination and irreversible chain transfer are absent.

  1. Ring-opening metathesis polymerizations should not be described as living if there is a non-zero probability of chain termination (e.g., due to side reactions consuming some part of the catalyst) or irreversible chain transfer (e.g., due to backbiting).

See living polymerization.

CP-125 metathesis polymerization

Polymerization in which unsaturated monomers are transformed into unsaturated polymers by a process of bond redistribution [1].

  1. Metathesis polymerization is most often metal-catalyzed and the kinetic-chain carriers alternate between metal-carbene complexes and metallacyclobutanes or between metal-carbyne complexes and metallacyclobutenes.

  2. The two most common forms of metathesis polymerization are ring-opening metathesis polymerization (ROMP) and acyclic diene metathesis polymerization (ADMET). ADMET is not a chain polymerization.

CP-126 ring-opening metathesis polymerization (ROMP)

Metathesis polymerization in which an unsaturated cyclic monomer is converted into an unsaturated monomeric unit that is either acyclic or contains fewer rings than the cyclic monomer [1].

  1. In general, ring-opening metathesis polymerizations that show some living characteristics should not be called living ring-opening metathesis polymerization when there are side reactions leading to loss of catalyst or irreversible chain transfer.

See metathesis polymerization, ring-opening polymerization.

CP-127 electron-transfer ring-opening metathesis polymerization (ET-ROMP)

Ring opening metathesis polymerization (ROMP) proceeding through one-electron redox processes in the absence of a metal carbene initiator.

  1. ET-ROMP may be initiated by single electron-transfer to a vinyl ether from a photoredox catalyst or by electrochemical processes to create a radical cation as the kinetic-chain carrier.

12 Coordination polymerization

A simplified mechanism for coordination polymerization when it involves a metal complex as the catalyst is provided in Scheme 17.

Scheme 17: 
          Simplified mechanism for coordination polymerization. Monomer is sequentially coordinated and inserted into the [Mt]–Pn bond. [Mt] is a metal complex that comprises the catalytic site, M is a monomer, P is a monomer unit.
Scheme 17:

Simplified mechanism for coordination polymerization. Monomer is sequentially coordinated and inserted into the [Mt]–Pn bond. [Mt] is a metal complex that comprises the catalytic site, M is a monomer, P is a monomer unit.

A distinction is made between activated-monomer polymerization, where the monomer is activated by coordination with a catalyst or activator, and coordination polymerization, where both the monomer and the propagating species form part of a coordination complex.

Coordination polymerization applied to olefins is often known as Ziegler-Natta polymerization. However, Ziegler-Natta polymerization is not a clearly defined term in the literature. Some use this to refer only to those polymerizations which make use of a heterogeneous catalyst. Others use the term only to refer to those polymerizations that make use of the particular form of heterogeneous catalyst defined in the early work of Ziegler and Natta. Named polymerization reactions are deprecated in IUPAC terminology.

The catalyst in coordination polymerization is the species that comprises the active site. The precursor to that species (often called a precatalyst) is often also incorrectly called a catalyst. The catalyst precursor could be called an initiator. The mechanisms of coordination-addition polymerization and coordination-insertion polymerization and ring-opening coordination polymerization are shown in Schemes 18, 19, and 20, respectively. In coordination-insertion polymerization (Scheme 19), the active site is a coordinatively unsaturated metal complex containing a metal-carbon or metal-hydride bond into which monomer is inserted through a metallacyclobutane transition state, thereby regenerating the active site.

Scheme 18: 
          Mechanism for coordination-addition polymerization of an acrylamide with a zirconium complex. L are ligands, R are alkyl substituents.
Scheme 18:

Mechanism for coordination-addition polymerization of an acrylamide with a zirconium complex. L are ligands, R are alkyl substituents.

Scheme 19: 
          Mechanism for catalyst formation in coordination-insertion polymerization of ethylene by the reaction of catalyst precursor (precatalyst) and cocatalyst. Mt is a metal, L are ligands, X is typically a halogen, R is alkyl or the growing chain, and □ is an empty orbital for alkene coordination.
Scheme 19:

Mechanism for catalyst formation in coordination-insertion polymerization of ethylene by the reaction of catalyst precursor (precatalyst) and cocatalyst. Mt is a metal, L are ligands, X is typically a halogen, R is alkyl or the growing chain, and □ is an empty orbital for alkene coordination.

Scheme 20: 
          
            Chain-propagation step in ring-opening coordination polymerization of caprolactone.
Scheme 20:

Chain-propagation step in ring-opening coordination polymerization of caprolactone.

CP-128 coordination polymerization

Chain polymerization that involves the preliminary coordination of a monomer molecule with a chain carrier [1].

  1. Coordination polymerization often occurs by pseudo-ionic polymerization.

  2. The term “metal-catalyzed polymerization” without explanation to designate coordination polymerization is deprecated.

CP-129 coordination-addition polymerization

Coordination polymerization of α,β-unsaturated amides or esters that proceeds by sequential monomer coordination and Michael addition events.

CP-130 coordination-insertion polymerization

insertion polymerization

polyinsertion

Coordination polymerization of olefins that proceeds by insertion of the olefin into a metal–carbon bond

See also insertion polymerization.

CP-131 living coordination polymerization

Coordination polymerization in which chain termination and irreversible chain transfer are absent.

  1. Coordination polymerizations, controlled coordination polymerizations and reversible-deactivation coordination polymerizations should not be described as living if there is a non-zero probability of chain termination or irreversible chain transfer.

  2. The use of the adjective living to denote systems with an extended catalyst lifetime is deprecated.

See living polymerization.

CP-132 reversible-deactivation coordination polymerization (RDCP)

Reversible-deactivation polymerization in which the chain carriers are coordination complexes.

  1. Examples of reversible-deactivation coordination polymerization are coordinative chain-transfer polymerization (CCTP) and chain-shuttling polymerization (CSP).

See reversible-deactivation polymerization.

CP-133 coordination ring-opening polymerization

Coordination polymerization in which a cyclic monomer yields a monomeric unit that is either acyclic or contains fewer rings than the cyclic monomer.

See ring-opening polymerization.

13 Sub-classes of coordination polymerization

A variety of forms of coordination polymerization have been described. Reversible coordinative chain-transfer polymerization (Scheme 21) and chain-shuttling polymerization (Scheme 22) are degenerative chain-transfer polymerizations, forms of reversible-deactivation polymerization.

Scheme 21: 
          Simplified mechanism for reversible coordinative chain-transfer polymerization. [Mt] is a metal complex and [CTA] is a chain-transfer agent. Monomer units are sequentially inserted into the [M]–Pn bond.
Scheme 21:

Simplified mechanism for reversible coordinative chain-transfer polymerization. [Mt] is a metal complex and [CTA] is a chain-transfer agent. Monomer units are sequentially inserted into the [M]–Pn bond.

Scheme 22: 
          Simplified mechanism for chain-shuttling polymerization (CSP). [Mt1] and [Mt2] are metal complexes and [CTA] is a chain-transfer agent. The propagating chain is “shuttled” between the two catalysts by way of the CTA.
Scheme 22:

Simplified mechanism for chain-shuttling polymerization (CSP). [Mt1] and [Mt2] are metal complexes and [CTA] is a chain-transfer agent. The propagating chain is “shuttled” between the two catalysts by way of the CTA.

CP-134 chain-shuttling polymerization (CSP)

Coordinative chain-transfer polymerization that involves two different catalysts showing different specificity, where chain propagation occurs sequentially on the two catalysts, allowing for the formation of segmented or multiblock copolymers.

  1. chain-shuttling polymerization is a form of degenerative chain-transfer polymerization (DTP).

See also coordinative chain-transfer polymerization, degenerative chain-transfer polymerization.

CP-135 chain-walking polymerization (CWP)

Coordination polymerization in which the chain carrier migrates along the formed polymer chain through a series of β-hydrogen eliminations and reinsertions with inversion of stereochemistry.

  1. In contrast to classical coordination polymerizations, which provide linear polyethylene, CWP of ethylene leads to a branched polymer.

  2. CWP of α-olefins generally leads to less branched polymers than those formed by classical coordination polymerization.

  3. Examples of CWP catalysts are aryl-substituted α-diimine-palladium(II) complexes [17].

CP-136 coordinative chain-transfer polymerization (CCTP)

Coordination polymerization in which a propagating chain is able to transfer reversibly between the catalyst and a chain-transfer agent, thereby converting the active species into a dormant species.

  1. coordinative chain-transfer polymerization is a form of degenerative chain-transfer polymerization (DTP).

See also chain-shuttling polymerization, degenerative chain-transfer polymerization.

CP-137 heterogeneous catalysis coordination polymerization

heterogeneous coordination polymerization

deprecated: Ziegler-Natta polymerization

Coordination polymerization making use of a heterogeneous catalyst.

  1. Heterogeneous catalysis coordination polymerization of polyolefins is sometimes known as Ziegler-Natta polymerization. Named reactions are deprecated in IUPAC terminology.

  2. When using the term heterogeneous coordination polymerization, the context must allow distinction from a coordination polymerization in a heterogeneous medium.

CP-138 homogeneous catalysis coordination polymerization

homogeneous coordination polymerization

Coordination polymerization making use of a homogeneous catalyst.

  1. Metallocene polymerization is one form of homogeneous coordination polymerization.

  2. When using the term homogeneous coordination polymerization, the context must allow distinction from a coordination polymerization in a homogeneous medium.

CP-139 metallocene polymerization

Coordination polymerization making use of a metallocene catalyst.

CP-140 pseudo-ionic polymerization

Polymerization proceeding by insertion of a monomer into a polar bond without the generation of ions [1].

  1. Most pseudo-ionic polymerizations involve concerted (e.g., four- or multi-centre) mechanisms of propagation.

  2. The term pseudo-ionic polymerization has been most often used in connection with ring-opening polymerization.

See also coordination polymerization.

CP-141 rare-earth-metal-mediated coordination-addition polymerization

rare-earth-metal-mediated coordination polymerization

rare-earth-metal-mediated group-transfer polymerization

lanthanide-mediated group-transfer polymerization

Coordination-addition polymerization with propagation occurring within the coordination sphere of a rare-earth metal complex.

  1. The process may also involve non-rare-earth metal complexes with a sufficiently large coordination sphere (e.g., zirconium).

14 Condensative chain polymerization

Condensative chain polymerization was previously only defined within a note to the term chain polymerization [1, 3]. A general mechanism for the propagation step in condensative chain polymerization is shown in Scheme 23. Note that nucleophilic ring-opening polymerization of intramolecular anhydrides of N-carboxy amino acids (amino acid N-carboxy anhydrides) mentioned in [1, 3] is not usually considered as a condensative chain polymerization because carbon dioxide is not eliminated in the propagation step, but rather in a separate step following propagation.

Scheme 23: 
          Simplified mechanism for condensative chain polymerization.
Scheme 23:

Simplified mechanism for condensative chain polymerization.

CP-142 condensative chain polymerization (CCP)

Chain polymerization in which the individual propagation steps are condensation reactions.

  1. Condensative chain polymerization appears under a variety of names, which include: chain-growth condensation polymerization, chain-growth polycondensation, catalyst-transfer polymerization, catalyst-transfer condensation polymerization, catalyst-transfer polycondensation. The use of terms that indicate CCP to be a form of polycondensation is deprecated as being inconsistent with the IUPAC definition of that term [1, 3].

  2. An example is the polymerization of potassium 5-cyano-4-methyl-2-propylphenolate initiated by (4-fluorophenyl)(4-(trifluoromethyl)phenyl)methanone to make an aromatic polyether, in which KF is the condensate.

See also catalyst-transfer polymerization.

15 Forms of condensative chain polymerization

A mechanism for catalyst-transfer polymerization is shown in Scheme 24. The process is a condensative chain polymerization and can show living characteristics when reaction of the propagating species, an active polymer (A-Pn-B*), with monomer (A-M-B) is much faster that the self-reaction of monomer (A-M-B with A-M-B) or the active polymer (A-Pn-B* with A-Pm-B*). The process should not be called a living polymerization if it is complicated by side reactions.

Scheme 24: 
          Simplified mechanism for catalyst-transfer polymerization. -Cat-is a catalyst.
Scheme 24:

Simplified mechanism for catalyst-transfer polymerization. -Cat-is a catalyst.

CP-143 catalyst-transfer polymerization (CTP)

catalyst-transfer chain polymerization

Catalysed condensative chain polymerization where the catalyst is transferred from reactant polymer to product polymer with high efficiency.

  1. Examples of catalyst-transfer polymerization include catalyst-transfer cross-coupling polymerization and enzyme-catalyzed polymerizations to form, for example, polypeptides, DNA, and RNA.

  2. It is recommended that the adjective “chain” be included in the term catalyst-transfer chain polymerization in circumstances where there may be confusion with respect to whether a chain mechanism is involved.

CP-144 catalyst-transfer cross-coupling polymerization

Catalyst-transfer polymerization where the propagation steps comprise cross-coupling reactions.

  1. Examples of catalyst-transfer cross-coupling polymerization are:

    1. Kumada catalyst-transfer cross-coupling polymerization (KCTP), where the propagation steps comprise metal-catalyzed cross-coupling reactions of a Grignard reagent with an organic halide. The process is also known as Grignard metathesis (GRIM) polymerization.

    2. Suzuki−Miyaura catalyst-transfer cross-coupling polymerization, where the propagation steps comprise Pd-catalyzed cross-coupling reactions between an organoboron compound and an organic halide.

      Named polymerization reactions are deprecated in IUPAC terminology.

CP-145 living condensative chain polymerization

Condensative chain polymerization in which chain termination and irreversible chain transfer are absent.

  1. Condensative chain polymerizations should not be described as living if chain termination or irreversible chain transfer are evident.

16 Alphabetical index of terms

An alphabetical list of terms defined in this document is provided in Table 2. Deprecated terms are indicated. Additional terms mentioned in Notes are not included in this list. The Term Number indicated for synonyms, where these have a separate Term Number, is that of the synonym for which the term is defined.

Table 2:

Alphabetical Index of Terms.

Term Term Number
activated monomer CP-39
activated-monomer polymerization (AMP) CP-1
activation (in a chain polymerization) CP-61
activation (in ATRP) CP-55
activation (in SRMP) CP-54
activator (in activated-monomer polymerization) CP-40
activator (in ATRP) CP-41
activator (in coordination polymerization) CP-42
active centre (in a chain polymerization) CP-43
active macromolecule (in RDP) CP-44
active polymer chain CP-44
active site CP-43
addition-fragmentation chain transfer CP-45
aminoxyl-mediated polymerization CP-20
aminoxyl-mediated radical polymerization (AMRP) CP-20
anion-activated-monomer polymerization CP-122
anionic activated-monomer polymerization CP-122
anionic group-transfer polymerization CP-109
anionic polymerization CP-108
anionic ring-opening polymerization CP-110
atom-transfer radical polymerization (ATRP) CP-27
bimolecular chain activation CP-55
cage effect CP-47
carbonothioyl-mediated radical polymerization CP-26
catalyst CP-48
catalyst (in ATRP) (deprecated term) CP-41
catalyst (in coordination polymerization or ROMP) CP-49
catalyst precursor (in coordination polymerization) CP-50
catalyst-transfer chain polymerization CP-143
catalyst-transfer cross-coupling polymerization CP-144
catalyst-transfer polymerization (CTP) CP-143
catalytic chain termination CP-52
catalytic chain transfer (CCT) CP-51
cation-activated-monomer polymerization CP-123
cationic activated-monomer polymerization CP-123
cationic polymerization CP-116
cationic ring-opening polymerization CP-117
chain activation CP-53
chain activation (in ATRP) CP-55
chain activation (in DTRP) CP-56
chain activation (in SRMP) CP-54
chain carrier (in polymerization) CP-57
chain deactivation CP-58
chain initiation CP-59
chain polymerization CP-2
chain propagation (in a chain polymerization) CP-60
chain reaction CP-3
chain reactivation CP-61
chain termination (in a chain polymerization) CP-62
chain transfer CP-63
chain-shuttling polymerization (CSP) CP-134
chain-transfer agent (CTA) CP-64
chain-transfer agent (CTA) (in RAFT polymerization) CP-97
chain-walking polymerization (CWP) CP-135
cobalt-mediated radical polymerization (CMRP) CP-21
cocatalyst (in coordination polymerization) CP-42
combination CP-66
condensative chain polymerization (CCP) CP-142
controlled anionic polymerization CP-111
controlled cationic polymerization CP-118
controlled ionic polymerization CP-103
controlled polymerization CP-4
controlled radical polymerization (CRP) CP-15
controlled reversible-deactivation polymerization CP-10
coordination polymerization CP-128
coordination ring-opening polymerization CP-133
coordination-addition polymerization CP-129
coordination-insertion polymerization CP-130
coordinative chain-transfer polymerization (CCTP) CP-136
cyclopolymerization CP-5
deactivator (in ATRP) CP-67
dead polymer chain CP-68
degenerate chain transfer CP-69
degenerate chain-transfer radical polymerization CP-32
degenerate transfer CP-70
degenerate-transfer polymerization CP-6
degenerative chain transfer CP-70
degenerative chain-transfer radical polymerization (DTRP) CP-32
degenerative transfer CP-70
degenerative-transfer polymerization (DTP) CP-6
disproportionation (in a chain polymerization) CP-71
dormant macromolecule (in RDP) CP-72
dormant polymer chain CP-72
dormant species CP-72
electron-transfer ring-opening metathesis polymerization (ET-ROMP) CP-127
electrophilic chain polymerization CP-119
group-transfer polymerization (GTP) CP-7
growing chain CP-73
heterogeneous catalysis coordination polymerization CP-137
heterogeneous coordination polymerization CP-137
homogeneous catalysis coordination polymerization CP-138
homogeneous coordination polymerization CP-138
immortal polymerization (deprecated term) CP-9
inactive chain CP-74
inactive macromolecule (in RDP) CP-74
inhibition (in polymer science) CP-75
inhibitor (in polymer science) CP-76
inifer CP-77
iniferter CP-78
iniferter process CP-22
initialization (in coordination polymerization or ROMP) CP-80
initialization (in RDP) CP-79
initialization efficiency (in RDP) CP-82
initializer (in RDP) CP-81
initiating species CP-83
initiation CP-59
initiation (in a chain polymerization) CP-84
initiator CP-85
initiator (in coordination polymerization) CP-50
initiator efficiency (for initiation of polymerization) (f, fi) CP-86
inner-sphere electron transfer atom-transfer radical polymerization (ISET-ATRP) CP-28
insertion polymerization CP-8
iodine-transfer polymerization (ITP) CP-33
ionic chain polymerization CP-104
ionic polymerization CP-104
ionic ring-opening polymerization CP-105
irreversible chain deactivation CP-62
kinetic-chain carrier CP-87
living anionic polymerization CP-112
living cationic polymerization CP-120
living condensative chain polymerization CP-145
living coordination polymerization CP-131
living ionic polymerization CP-106
living polymer chain CP-88
living polymerization CP-9
“living polymerization” (deprecated term when quotation marks used) CP-9
living radical polymerization CP-16
“living radical polymerization” (deprecated term when quotation marks used) CP-16
living ring-opening metathesis polymerization CP-124
macro-chain-transfer agent (macroCTA) CP-89
macroinitiator CP-90
macroRAFT agent (in RAFT polymerization) CP-89
mediating agent CP-91
mediator CP-91
metallocene polymerization CP-139
metathesis polymerization CP-125
nitroxide-mediated (radical) polymerization (NMP) (deprecated term) CP-20
non-metal-mediated atom-transfer radical polymerization (NM-ATRP) CP-29
non-propagating species CP-74
non-propagating species CP-92
nucleophilic chain polymerization CP-114
organobismuthane-mediated radical polymerization (BIRP) CP-34
organometallic-mediated radical polymerization (OMRP) CP-23
organostibane-mediated radical polymerization (SBRP) CP-35
organotellurium-mediated radical polymerization (TERP) CP-36
outer-sphere electron transfer ATRP (OSET-ATRP) CP-30
polyaddition CP-13
polycondensation CP-14
polyinsertion CP-8
polymerization CP-12
precatalyst (in coordination polymerization) CP-50
primary species (in a chain polymerization) CP-93
propagating species (in a chain polymerization) CP-94
propagation CP-60
pseudo-ionic polymerization CP-140
pseudo-living polymerization (deprecated term) CP-9
pseudo-living radical polymerization (deprecated term) CP-16
quasi-living polymerization (deprecated term) CP-9
quasi-living radical polymerization (deprecated term) CP-16
radical polymerization CP-17
radical ring-opening polymerization CP-18
rare-earth-metal-mediated coordination-addition polymerization CP-141
reactivation (in a chain polymerization) CP-61
retardation (in polymer science) CP-95
retarder (in polymer science) CP-96
reverse iodine-transfer polymerization (RITP) CP-37
reversible-addition-fragmentation chain-transfer agent (RAFT agent) CP-97
reversible-addition-fragmentation chain-transfer polymerization (RAFT polymerization) CP-38
reversible-addition-fragmentation radical polymerization (RAFRP) CP-25
reversible-deactivation anionic polymerization (RDAP) CP-113
reversible-deactivation cationic polymerization (RDCP) CP-121
reversible-deactivation coordination polymerization (RDCP) CP-132
reversible-deactivation ionic polymerization (RDIP) CP-107
reversible-deactivation polymerization (RDP) CP-10
reversible-deactivation radical polymerization (RDRP) CP-19
ring-opening metathesis polymerization (ROMP) CP-126
ring-opening nucleophilic chain polymerization CP-115
ring-opening polymerization (ROP) CP-11
secondary species (in a chain polymerization) CP-98
single-electron-transfer living radical polymerization (SET-LRP) (deprecated term) CP-30
single-electron-transfer RDRP (SET-RDRP) CP-30
stable radical (in SRMP or RAFRP) CP-99
stable-free-radical-mediated polymerization (SFRMP) (deprecated term) CP-24
stable-radical-mediated polymerization (SRMP) CP-24
substitution chain transfer CP-102
termination CP-62
transfer CP-63
transfer agent CP-64
transition-metal-mediated living radical polymerization (deprecated term) CP-31
transition-metal-mediated radical polymerization CP-31
transition-metal-mediated reversible-deactivation radical polymerization CP-31
unimer CP-100
unimolecular activation CP-54
unimolecular chain activation CP-54
Ziegler-Natta polymerization (deprecated term) CP-137

17 Acronyms, initialisms, abbreviations, and symbols

Table 3 provides a summary of acronyms, initialisms, abbreviations, and symbols for terms defined in this document.

Table 3:

Acronyms, Initialisms, abbreviations, and symbols.

Acronyma Term Term Number
AMP activated-monomer polymerization CP-1
AMRP aminoxyl-mediated radical polymerization CP-20
ATRP atom-transfer radical polymerization CP-27
BIRP organobismuthane-mediated radical polymerization CP-34
CCP condensative chain polymerization CP-142
CCT catalytic chain transfer CP-51
CCTP coordinative chain-transfer polymerization CP-136
CMRP cobalt-mediated radical polymerization CP-21
CRP controlled radical polymerization CP-15
CSP chain-shuttling polymerization CP-134
CTA chain-transfer agent CP-64
CTP catalyst-transfer polymerization CP-143
CWP chain-walking polymerization CP-135
DTP degenerative-transfer polymerization CP-6
DTRP degenerative chain-transfer radical polymerization CP-32
ET-ROMP electron-transfer ring-opening metathesis polymerization CP-127
f initiator efficiency CP-86
f i initiator efficiency for initiation of polymerization CP-86
GTP group-transfer polymerization CP-7
ISET-ATRP inner-sphere electron transfer atom-transfer radical polymerization CP-28
ITP iodine-transfer polymerization CP-33
macroCTA macro-chain-transfer agent CP-89
NM-ATRP non-metal-mediated atom-transfer radical polymerization CP-29
NMP nitroxide-mediated radical polymerization (deprecated term) CP-20
OMRP organometallic-mediated radical polymerization CP-23
OSET-ATRP outer-sphere electron transfer ATRP CP-30
RAFRP reversible-addition-fragmentation radical polymerization CP-25
RAFT agent reversible-addition-fragmentation chain-transfer agent CP-97
RAFT polymerization reversible-addition-fragmentation chain-transfer polymerization CP-38
RDAP reversible-deactivation anionic polymerization CP-113
RDCP reversible-deactivation cationic polymerization CP-121
RDCP reversible-deactivation coordination polymerization CP-132
RDIP reversible-deactivation ionic polymerization CP-107
RDP reversible-deactivation polymerization CP-10
RDRP reversible-deactivation radical polymerization CP-19
RITP reverse iodine-transfer polymerization CP-37
ROMP ring-opening metathesis polymerization CP-126
ROP ring-opening polymerization CP-11
SBRP organostibane-mediated radical polymerization CP-35
SET-LRP single-electron-transfer living-radical polymerization (deprecated term) CP-30
SET-RDRP single-electron-transfer RDRP CP-30
SFRMP stable-free-radical-mediated polymerization (deprecated term) CP-24
SRMP stable-radical-mediated polymerization CP-24
TERP organotellurium-mediated radical polymerization CP-36
  1. aAcronyms, initialism, abbreviation, or symbol.

18 Memberships of sponsoring bodies

Membership of the IUPAC Polymer Division Committee for the period 2020–2021 is as follows:

President: C. K. Luscombe (USA); Vice President: I. Lacik (Slovakia); Secretary: P. D. Topham; Past President: G. T. Russell (New Zealand); Titular Members: M. C. H. Chan (Malaysia); C. M. Fellows (Australia); R. C. Hiorns (France); R. Hutchinson (Canada); D. S. Lee (South Korea); J. B. Matson (USA); Associate Members: S. Beuermann (Germany); C. dos Santos (Brazil); G. Moad (Australia); M. Peeters (UK); P. Théato (Germany); M. Walter (USA); National Representatives: A. Aguiar-Ricardo (Portugal); J. He (China); C.-S. Hsu (Taipei, China); A. Sturcova (Czech Republic); M. T. Kalagasidis Krušić (Serbia); P. E. Mallon (South Africa); O. Philippova (Russia); G. Raos (Italy); M. Sawamoto (Japan); J. van Hest (Netherlands).

Membership of the Subcommittee on Polymer Terminology during the preparation of these Recommendations (2009–2020) was as follows:

Chair: R. G. Jones (UK), 2006–2013; R. C. Hiorns (France), from 2014; Secretary: T. Kitayama (Japan), 2008–2009; R. C. Hiorns (France), 2010–2013; C. K. Luscombe (USA), 2014–2015; P. D. Topham (UK), from 2016; Members: V. Abetz (Germany); R. Adhikari (Nepal); G. Allegra (Italy); M. Barón (Argentina); R. Boucher (UK); B. Brettmann (USA); P. Carbone (UK); M. C. H. Chan (Malaysia); T. Chang (Korea); J. Chen (USA); W. Farrell (USA); C. M. Fellows (Australia); A. Fradet (France); C. F. O. Graeff (Brazil); D. Haase (USA); J. He (China); K. H. Hellwich (Germany); J-L. Gardette (France); M. Hess (Germany); P. Hodge (UK); W. Hu (China); A. D. Jenkins (UK); J. I. Jin (Korea); J. Kahovec (Czech Republic); D. J. Keddie (UK); T. Kitayama (Japan); P. Kratochvíl (Czech Republic); P. Kubisa (Poland); M. Malinconico (Italy); P. Mallon (South Africa); J. B. Matson (USA); S. V. Meille (Italy); J. Merna (Czech Republic); G. Moad (Australia); W. Mormann (Germany); T. Nakano (Japan), C. K. Ober (USA); M. Peeters (UK); S. Penczek (Poland); O. Philippova (Russia); M. D. Purbrick (UK); G. Raos (Italy); G. Russell (USA); C. dos Santos (Brazil); C. Scholz (USA); F. Schué‡ (France); S. Słomkowski (Poland); D. W. Smith (USA), L. Sosa Vargas (France); R. F. T. Stepto‡ (UK); N. Stingelin (UK); A. Sturcova (Czech Republic); D. Tabak (Brazil); P. Théato (Germany); J. P. Vairon (France); M. Vert (France); J. Vohlídal (Czech Republic); M. G. Walter (USA); E. S. Wilks (USA); W. J. Work (USA); A. Yerin (Russia); M.-H. Yoon (Korea).


Corresponding author: Graeme Moad, CSIRO Manufacturing, Clayton, VIC3168, Australia, E-mail:

Deceased (1939–2021).

Article note: Sponsoring bodies: IUPAC Polymer Division, Sub-Committee on Polymer Terminology.


Funding source: IUPAC

Award Identifier / Grant number: 2010-007-1-400

Acknowledgements

We are grateful for the contributions of Phil Hodge, Premislav Kubisa, Jean-Pierre Vairon, and the late Bob Stepto for their support during the inception of this project. We are also grateful for the input of Theoni Georgiou (Imperial College, London) with respect to terminology for group transfer polymerization. This document is dedicated to our coauthor Richard Glyn (Dick) Jones (1939–2021).

  1. Research funding: This work was prepared under project 2010-007-1-400 of IUPAC (Funder ID: 10.13039/100006987).

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Received: 2020-12-19
Accepted: 2022-06-09
Published Online: 2022-10-24
Published in Print: 2022-09-27

© 2022 IUPAC & De Gruyter. This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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